1. Field of Invention
The invention concerns a printing machine having at least a central impression cylinder, to which several inking units are allocated, in which a printing material sheet can be supplied to the impression cylinder in the area between the first inking unit and the last inking unit along a feed path.
2. Description of the Prior Art
Printing machines with a central impression cylinder and inking units arranged around it are adequately known and are used mostly to print sheet-like printing materials according to the flexographic printing method. These sheet-like printing materials are generally used to produce packaging.
The sheet-like material can be unwound for this purpose from an unwinding station and fed to the impression cylinder on a feed path. The area between the unwinding station and the impression cylinder is generally passable. This is important, in particular, in order to be able to supply the unwinding station with a new sheet reel, when the previous sheet reel is used up. However, this area must also be passable by operating personnel for sheet observation.
Since flexographic printing is a letterpress method, the areas being printed are raised relative to the areas not being printed. The transition between areas not being printed and the areas being printed is referred to as starting edge. The areas being printed are made from flexible material, which is generally slightly compressed when the starting edge strikes the printing material. The material expands when the area being printed is no longer in contact with the printing material.
This dynamic causes oscillations of the plate that the areas being printed represent. These oscillations propagate as sound into the surroundings, so that a significant noise burden can occur in the area of the printing machine. The noise level can surpass the acceptable burden for operating personnel precisely in the passable area described in the previous paragraph between the unwinding station and the impression cylinder.